The present invention relates to a driving device for signs having movable display screens which are multilateral and simultaneously rotatable by means of a driving unit for providing together a number of continuously recurrent pictures corresponding to the number of sides on the display screens. Specifically at least some of the display screens include two toothed pulleys of which one is adapted to cooperate with a toothed belt for transferring the driving power of the driving unit from a preceding display screen and the other is adapted to cooperate with another toothed belt for transferring the driving power to a succeeding display screen.
With signs of the abovementioned type it is important to be able to quickly set the display screens in exact relations to each other. Hitherto, it has not been possible to perform such setting operations quickly and without causing any problem, because present toothed pulleys have been difficult to get at for clamping and loosening. It has also been difficult to attain exact setting of the toothed pulleys relative to each other, because it has been necessary to loosen several pulleys at the same time and thereafter hold them in an exact mutual relationship until they are once again clamped. Since it is often necessary to perform the setting operations high up on scaffolds and in bad weather, these problems have further increased.
The object of the present invention has been to eliminate the above problems and provide a device which substantially facilitates the procedure of setting the display screens in exact positions relative to each other.
The present invention permits easy access to the clamping device of the toothed pulleys from the front of the sign by means of a simple tool for clamping and loosening said pulleys and it is possible to loosen and clamp both pulleys in each display screen simultaneously without the risk of displacement of said screens relative to each other.